Hello Paul / Helen,
Walked a variant of your
St Fillans Hill route last weekend and thought I should mention that the fisherman's path mentioned for the first sentence of Stage 2 is no longer visible (at all - I couldn't see it leave the road, or rejoin later on, and I went down to the river in the middle of the section to look for it too and still couldn't find it), so you have to stay on the road. Also mentioned in someone else's walk report from 2012 so seems like it's gone for good.
Also, there's now public parking opposite the footbridge over the River Earn and opposite the Drummond Hotel, so you don't need to park at the west end of the village. (Although we actually parked on the south bank road.)
On the plus side... no mud at the moment!!